<!DOCTYPE HTML>
<html>
<head>
<title>OffscreenCanvas webgl still updates after canvas resize.</title>
<style type="text/css">
.nomargin {
  margin: 0px auto;
}
</style>
</head>
<body onload="main()">
<div id="container" style="position:absolute; top:0px; left:0px">
<canvas id="output" width="100" height="100" class="nomargin"></canvas>
</div>
<script>
//  Correct end result of this test: A vertical green rectangle.
function main() {
  var canvas = document.getElementById('output');
  var offscreen = canvas.transferControlToOffscreen();
  var gl = offscreen.getContext('webgl');
  gl.clearColor(1.0, 0.0, 0.0, 1.0);
  gl.clear(gl.COLOR_BUFFER_BIT);
  requestAnimationFrame(() => {
    // nested rAF to ensure initial frame is pushed before resize attempt
    requestAnimationFrame(() => {
      offscreen.width = 50;
      requestAnimationFrame(() => {
        gl.clearColor(0.0, 1.0, 0.0, 1.0);
        gl.clear(gl.COLOR_BUFFER_BIT);
        waitForFinish();
      });
    });
  });
}

var g_swapsBeforeAck = 15;

function waitForFinish()
{
  if (g_swapsBeforeAck == 0) {
    domAutomationController.send("SUCCESS");
  } else {
    g_swapsBeforeAck--;
    requestAnimationFrame(waitForFinish);
  }
}
</script>
</body>
</html>
